Ventilation & Oxygenation

Question 1

What is “breathing”?

Answer 1

Breathing is the movement of air in and out of the lungs

• Controlled by metabolic needs of the body. The levels of oxygen and carbon dioxide in the blood are prime examples. Chemoreceptor input describes how the central nervous system perceives these levels and acts upon them
• Breathing is under voluntary control in patients that are conscious and alert

Question 2

What is “ventilation”?

Answer 2

Ventilation is the aspect of breathing that refers to the actual movement of air in and out of the lungs

• Ventilation is determined by the tidal volume and the ventilatory rate
• Patients that are alert and breathing spontaneously can vary the amount of air that is inhaled and exhaled each time. They can control their respiratory rate
• Yawning and sighing are normal variations during the act of ventilation

Question 3

What is “respiration”?

Answer 3

Respiration is the actual use of inspired oxygen at the cellular level

• There is removal at the cellular level of carbon dioxide and metabolic wastes, especially the metabolic acids of lactic acid and ketoacids
• There are two variables responsible for cellular respiration:
  
  • Perfusion of capillaries with oxygen and blood rich in nutrients.
  • Venous blood flow that removes the cellular metabolic wastes to the heart, lungs and kidney

Question 4

What are the 4 physiological changes that occur with aging?

Answer 4

1. Reduced lung elasticity and increased ventilation-perfusion mismatching
2. There is reduced compliance in chest wall compliance and decrease in both diaphragmatic and intercostal muscle strength
3. Airway secretions are more difficult to clear
4. There is an altered responsiveness to both hypoxemia and hypercarbia

Question 5

What are 5 co-morbidities that can increase the risk of respiratory failure in the geriatric population?

Answer 5

1. Heart Failure
2. COPD
3. Dementia
4. Chronic inactivity
5. Chronic kidney disease

Question 6

What is ventilatory failure and how do you assess it?

Answer 6

• It is the absence or inadequate movement of oxygen into the lungs and/or of carbon dioxide out of the lungs
• Ventilatory failure is best assessed by measurement of the partial pressure of carbon dioxide on an ABG (PaCO2) and/or by measuring end-tidal CO2 levels

Question 7

What is apnea?

Answer 7

Apnea refers to the absence of the movement of respiratory gases

Question 8

What is hyponea?

Answer 8

Hypopnea refers to the inadequate movement of respiratory gases

Question 9

What is waveform capnography?

Answer 9

Waveform capnography represents the amount of carbon dioxide (CO2) in exhaled air, which assesses ventilation. It consists of a number and a graph. The number is capnometry, which is the partial pressure of CO2 detected at the end of exhalation

Question 10

What is the normal end-tital CO2?

Answer 10

35-45

Question 11

What are 2 common causes of ventilatory failure

Answer 11

1. Overdose of medications including sedatives, hypnotics and opioids where the body is unable to respond to the metabolic and cellular respiratory needs because of the influence of these drugs.

• The elderly population is particularly susceptible to suffering respiratory depression with the use of these drugs. Overdose can be unintentional as seen with iatrogenic over sedation in patients with COPD or intentional.
• Examples of intentional overdose include iatrogenic sedation with the intent to control ventilation and the drug overdose with suicidal intent.

2. The inability to get oxygen into and carbon dioxide out of the lungs can by acquired due to the pathology of the following conditions and/or diseases:

• Pulmonary infections, especially in patients with COPD
• Neuromuscular diseases including myasthenia gravis in crisis, Guillain-Barre syndrome and traumatic head or spinal cord injury
• Pulmonary edema of both cardiogenic and non-cardiogenic origin